Labour released figures that show the return of economic growth has overwhelmingly benefited the top 1% of earners.

The disclosure of the findings from HM Revenue and Customs precedes the announcement of employment and earnings statistics on Wednesday which are expected to reveal a buoyant economy.

Over the past year, the share of national post-tax income of the top 1% of taxpayers – just 300,000 people – has risen from 8.2% in 2012-13 to 9.8 % in 2013-14. Over the same period, the bottom 90% – a total of 27 million taxpayers – have seen their share of post-tax income fall from 71.3% to 70.4%, according to estimates contained in the latest Income Tax Liabilities Statistics published by HMRC. They cover the year when GDP growth returned and the top rate of income tax on earnings above £150,000 was reduced from 50% to 45%.

Labour will use the figures to argue that there has been no recovery for middle Britain. Chris Leslie, shadow chief secretary to the Treasury, said: "David Cameron and George Osborne are trying to claim the cost-of-living crisis is over, but these official figures expose what's really happening under the Tories. While the top 1% of taxpayers have seen their share of income after tax go up, the bottom 90% on middle and lower incomes have seen theirs fall.

"With the help of a huge tax cut from this government, the very richest are feeling a recovery, but everyone else is being left behind as growth finally returns.

"What we need is a recovery for the many, not just a few at the top. That's why we need to reform our economy to mend the broken link between the wealth of the nation and the living standards of hardworking Britain."

The raft of labour market statistics published on Wednesday will be studied to see how quickly unemployment is likely to fall below its pre-crisis levels. The rate in the three months to February stood at 6.9%, down sharply from a year ago but still well above its pre-crisis level of about 5%.

New immigration numbers are likely to show that as many as 30,000 extra Romanians and Bulgarians were working in the UK in the first three months of this year compared with the same period in 2013. The remaining restrictions on Romanians and Bulgarians working in the UK were lifted on 1 January.

The figures will cast further doubt on the Conservative pledge to cut net migration to below 100,000 by the time of next year's general election. Net migration -–the number coming to the UK for at least a year, minus the numbers leaving – rose 58,000 to 212,000 in the year to September 2013.

The prime minister told the liaison committee of MPs on Tuesday that the target was still perfectly achievable, but declined to give a date by which it would be met.

Keith Vaz, who chairs the Commons home affairs committee, cited the forecast of an extra 30,000 Romanians and Bulgarians as he pressed Cameron to admit that he was not going to meet that target by May 2015.

But Cameron insisted: "The target remains. I think it is absolutely achievable". He said the recent increase in net migration had largely been caused by an increase in migration from France, Portugal and Spain, rather than the new EU accession countries.

Cameron resisted pressure to end the inclusion of foreign students in the net migration statistics, which has helped hold the figure down but has been blamed by critics for cutting the overseas income of UK colleges. He insisted that the fall in overall numbers of foreign students was driven by action to shut down 700 "bogus" colleges and cited statistics showing that numbers of genuine overseas students at British universities had risen from 142,000 to 162,000 since 2010.

He said it was the task of British universities to go out and sell the great offer of being able to study in the UK and then to stay on in a graduate job.

He said: "No EU national has unrestricted access to the UK; they've got to be working, studying or self-sufficient. We need to get back to what the 'freedom of movement' was originally about - to move and take a job."

The UK Independence party's policy was, he said, "put the barricades up and pretend that these organisations don't work".

He said was happy to look at the way in which migrant statistics were gathered, admitting that a relatively small sample of people travelling in and out of the UK was used.

• This article was amended on 8 July 2014 to make clear that it is the share of post tax income which has fallen.